@Test
    void testFileSource() {
        NullPointerException e = assertThrows(
                NullPointerException.class,
                () -> new FileSource((File) null),
                "Should fail, since you must specify a file");
        assertEquals("file cannot be null", e.getMessage());
    }

    @Test
    void testGetInputStream() throws Exception {
        File txtFile = new File("target/test-classes/source.txt");